Definition of: pernicious

(pər·nish′əs) adjective
1. Having the power of destroying or injuring; tending to kill or hurt; very injurious; deadly.
2. Malicious; wicked. [<OF pernicieux <L perniciosus <pernicies destruction <per- thoroughly + nex, necis death]
—per·ni′cious·ly adverb
—per·ni′cious·ness noun Synonyms: bad, baneful, deadly, destructive, evil, harmful, hurtful, injurious, mischievous, noxious, perverting, ruinous. Pernicious is stronger than injurious; that which is injurious is capable of doing harm; that which is pernicious is likely to be destructive. See BAD, INIMICAL, NOISOME. Antonyms: advantageous, beneficial, favorable, good, healthful, helpful, profitable, salutary, serviceable, wholesome.